The present invention relates to impact beams made of pultruded reinforced polymeric material, and more particularly relates to a pultruded beam having a significant percentage of long continuous fiber reinforcement and that is optimized for impact, adapting it for use as vehicle bumper impact beams. The present invention also relates to apparatus and methods for making same. However, the present invention is not believed to be limited to only bumper impact beams, but instead is believed to extend to other impact beams and other products where properties are important such as bending strength, tensile strength, impact strength, strength to weight ratio, and/or attachment.
Modern vehicles include bumper beams designed for impact strength, but are also designed for designed low weight, high strength to weight ratio, front end aesthetics, optimal energy absorption, occupant safety, pedestrian injury reduction, flexible design in styling, and many other factors. Notably, weight significantly affects vehicle mileage, especially given a bumper beam's size and its position in front of the vehicle tires. Original equipment manufacturers (i.e. vehicle “OEMs”) continue to desire a next level in performance improvement and cost/mass optimization. For example, some vehicle OEMs have specified bumper beams made by aluminum extrusion, doing so despite a cost penalty for material, despite a loss of some material strength properties, and despite functional and physical limitations of aluminum extruding processes and extruded components.
Pultruded components incorporate a high density of very-long or continuous reinforcement fibers in a polymeric part, such as 40-50% reinforcement or more. However, known pultruding processes and pultruded polymeric parts have not been accepted by OEMs for making bumper impact beams for several reasons. For example, pultruded materials can exhibit unacceptable characteristics on impact, such as premature catastrophic failure, (e.g. failure by fast-propagating longitudinally-extending cracks along lines defined by reinforcement fibers and polymeric material flow lines), low total energy absorption and low maximum energy absorption prior fracture, and generally unacceptable force-deflection profiles. Also, it is noted that pultrusion processes tend to be relatively slow, parts can be process sensitive, and the processes are not generally widely known nor widely used. Also, pultruded components require careful secondary treatment with care being necessary to avoid significant loss of properties due to breaking of imbedded fibers and/or creation of stress-risers when creating beam attachment sites. Also, distribution of fibers and their exact location and orientation can be difficult to control. Also, it is difficult to sweep (i.e. longitudinally curve) an elongated pultruded part. Still further, impact properties at corners and at other locations of “natural” stress risers can be problematic.